Powertrain, generic (extended)

P2A4D Alternative Fuel Temperature Sensor Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A4D means the voltage of the gas temperature sensor is below its valid limit. Gas temperature sensors are normally NTC thermistors whose resistance drops as they warm up, so a low voltage would correspond to extremely hot gas; in practice it nearly always means the signal wire is grounded or the sensor is shorted inside. TransEco shows how a gas module reacts to the comparable rail temperature Low code: dedicated installations replace the reading with the intake air temperature, bi-fuel ones are forced back to petrol, and the lamp comes on. No manufacturer lists P2A4D itself. Unplugging the sensor should make the reading jump to very cold; if it stays hot, look for the short in the harness rather than in the sensor.

Likely causes

Signal wire of the gas temperature sensor shorted to ground
Thermistor shorted internally
Moisture bridging the connector pins

Symptoms

  • Check engine light
  • Gas mode refused, bi-fuel vehicle runs on petrol
  • Live data shows an implausibly hot gas temperature

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–450
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

alt fuel temperature sensorwiring harnessafcm

Related codes

P2A4BP2A4EP2A4CP01B6P0182

References: law.cornell.edu, http:.